linux-kernel - Re: [PATCH v10 7/9] proc: move hidepid values to uapi as they are user interface to mount

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Message-ID: <202004031658.8D0C048E3@keescook>
Date:   Fri, 3 Apr 2020 16:59:23 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Alexey Gladkov <gladkov.alexey@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        Linux API <linux-api@...r.kernel.org>,
        Linux FS Devel <linux-fsdevel@...r.kernel.org>,
        Linux Security Module <linux-security-module@...r.kernel.org>,
        Akinobu Mita <akinobu.mita@...il.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Alexey Gladkov <legion@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Daniel Micay <danielmicay@...il.com>,
        Djalal Harouni <tixxdz@...il.com>,
        "Dmitry V . Levin" <ldv@...linux.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        "J . Bruce Fields" <bfields@...ldses.org>,
        Jeff Layton <jlayton@...chiereds.net>,
        Jonathan Corbet <corbet@....net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>
Subject: Re: [PATCH v10 7/9] proc: move hidepid values to uapi as they are
 user interface to mount

On Thu, Apr 02, 2020 at 11:58:28AM -0500, Eric W. Biederman wrote:
> 
> I will just say that I do not understand exporting this to the uapi
> headers.  Why do we want to export the enumeration names?
> 
> I understand that the values are uapi.  This looks like it will make it
> difficult to make changes that rename enumeration values to make
> the code more readable.
> 
> Given that this patchset goes immediately to using string enumerated
> values, I also don't understand the point of exporting
> HIDEPID_NOT_PTRACEABLE.  I don't think we need to ever let
> people use the numeric value.
> 
> My sense is that if we are switching to string values we should
> just leave the existing numeric values as backwards compatiblity
> and not do anything to make them easier to use.

Yeah, that's what I had suggested too. Let's not export this to UAPI.

-Kees

> 
> Eric
> 
> 
> Alexey Gladkov <gladkov.alexey@...il.com> writes:
> 
> > Suggested-by: Alexey Dobriyan <adobriyan@...il.com>
> > Reviewed-by: Alexey Dobriyan <adobriyan@...il.com>
> > Signed-off-by: Alexey Gladkov <gladkov.alexey@...il.com>
> > ---
> >  include/linux/proc_fs.h      |  9 +--------
> >  include/uapi/linux/proc_fs.h | 13 +++++++++++++
> >  2 files changed, 14 insertions(+), 8 deletions(-)
> >  create mode 100644 include/uapi/linux/proc_fs.h
> >
> > diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
> > index afd38cae2339..d259817ec913 100644
> > --- a/include/linux/proc_fs.h
> > +++ b/include/linux/proc_fs.h
> > @@ -7,6 +7,7 @@
> >  
> >  #include <linux/types.h>
> >  #include <linux/fs.h>
> > +#include <uapi/linux/proc_fs.h>
> >  
> >  struct proc_dir_entry;
> >  struct seq_file;
> > @@ -27,14 +28,6 @@ struct proc_ops {
> >  	unsigned long (*proc_get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
> >  };
> >  
> > -/* definitions for hide_pid field */
> > -enum {
> > -	HIDEPID_OFF	  = 0,
> > -	HIDEPID_NO_ACCESS = 1,
> > -	HIDEPID_INVISIBLE = 2,
> > -	HIDEPID_NOT_PTRACEABLE = 4, /* Limit pids to only ptraceable pids */
> > -};
> > -
> >  /* definitions for proc mount option pidonly */
> >  enum {
> >  	PROC_PIDONLY_OFF = 0,
> > diff --git a/include/uapi/linux/proc_fs.h b/include/uapi/linux/proc_fs.h
> > new file mode 100644
> > index 000000000000..dc6d717aa6ec
> > --- /dev/null
> > +++ b/include/uapi/linux/proc_fs.h
> > @@ -0,0 +1,13 @@
> > +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> > +#ifndef _UAPI_PROC_FS_H
> > +#define _UAPI_PROC_FS_H
> > +
> > +/* definitions for hide_pid field */
> > +enum {
> > +	HIDEPID_OFF            = 0,
> > +	HIDEPID_NO_ACCESS      = 1,
> > +	HIDEPID_INVISIBLE      = 2,
> > +	HIDEPID_NOT_PTRACEABLE = 4,
> > +};
> > +
> > +#endif

-- 
Kees Cook